DESCRIPTION (provided by investigator): There is an important need for validated, low-cost smoking cessation interventions that can reach large populations of smokers. Internet-based cessation programs can reach an increasingly large number of smokers. Approximately one third of all persons are Internet users; an estimated 8 million of them are cigarette smokers. Internet-based smoking cessation programs can be interactive, personalize information based on participant characteristics and interests, provide a high degree of choice and flexibility, and provide social support from both peers and professionals. While initial start-up costs can be high, interactive Internet interventions cost little to maintain, and provide 24-hour/7-day access to smoking cessation assistance. We will develop a comprehensive Internet smoking cessation program with three major components: (a) support for the use of efficacious pharmacological therapies (e.g., nicotine replacement therapy and Zyban), (b) a cognitive-behavioral skills development, and (c) social support (primarily via on-line forums and chat rooms), and evaluate it in a randomized control trial designed to assess the impact of the program. The control condition will be an exercise and nutrition program of proven efficacy (PACE+) designed for Internet use. This program serves as a credible attention-placebo control. Approximately 2000 persons will be enrolled from large worksites that provide intranet links (and high-bandwidth connections) to our website. All assessment will be accomplished via the Internet and much of the process data--use of various intervention elements and transcripts of discussion groups--is recorded and stored automatically. Seven-day point prevalence cessation at three- and six-month follow-ups will serve as the primary outcomes, augmented by other prevalence and sustained quit outcomes. A variety of subject characteristics and process measures will be examined as predictors or mediators. After outcomes are assessed at six months, participants will be given access to the contrasting condition and encouraged to enroll. Secondary analyses will examine the effectiveness of the PACE+ program. The proposed design will provide important practical information about effectiveness of a low-cost Internet intervention to assist smokers in stopping smoking.